A KC-135 Stratotanker refuels an F-16 Fighting Falcon. The Air Force conducted a critical design review of the KC-135s replacement, the KC-46, earlier this month. (SSgt Suzanne M. Day / Air Force)

The Air Force’s new tanker conducted its Critical Design Review (CDR) earlier this month and is on track to deliver a final report “well in advance” of a Sept. 24 due date, the service said in a Thursday statement.

The CDR was conducted July 8-10 at Boeing’s facility in Mukilteo, Wash.

“For the warfighter, completion of this milestone is a big step forward toward beginning the recapitalization of the Air Force’s legacy KC-135 fleet, delivering advanced and improved multimission capabilities to the fight on day one.” Maj. Gen. John Thompson, program executive officer for tankers, said in the statement.

“Earlier this month the Air Force led us through the tanker program’s critical design review. That process, conducted two-and-a-half months ahead of contract schedule, will validate that the design of the KC-46A meets the Air Force’s requirements,” Boeing said in a company statement. “Boeing believes the review went well and initial feedback from our customer has been positive. Final approval by the USAF is anticipated in the near future.”

Based on Boeing’s 767-200ER commercial plane, the KC-46 program will produce 179 new planes to replace the aging KC-135 tanker fleet, with 18 tankers expected by 2017 and production ending in 2027.

The program has hit a number of milestones this year, awarding a training contract in early May, choosing bases for the tankers later that month and beginning production on the first model in late June. Boeing expects to deliver the first tanker in 2016.

Air Force officials identified the new tanker as one of its three key modernization priorities, alongside the F-35 Joint Strike Fighter and a new long-range bomber.

The KC-46 program is the first part of a three-stage process that will eventually replace the entire Air Force tanker fleet.